Design and Synthesis of Chromone-based Fluorescent Probes for the Selective Determination of Ni²⁺

Aromatic heterocycles constitute an essential class of compounds in organic chemistry with broad applications in analytical and medicinal chemistry. Among them, chromone derivatives have emerged as valuable platforms for developing fluorescent and colorimetric probes due to their favorable photophysical properties. Concurrently, detecting transition metals remains a critical environmental and biological challenge. Although nickel is a vital trace element, its excessive accumulation causes toxicity, requiring the development of reliable, rapid, and sensitive detection methods.

In this work, we report the synthesis of novel heterocyclic chemosensors. Two hydrazone-chromone type ligands were successfully prepared through the condensation of 3-formylchromone with substituted hydrazones under mild conditions, yielding 40–60% after purification. These compounds were designed as fluorescent probes for the selective recognition of Ni²⁺ ions in solution. The proposed sensing mechanism relies on the coordination of the metal center with the oxygen and nitrogen heteroatoms of the ligand. The structures of the synthesized products were fully confirmed using standard spectroscopic techniques, including infrared (IR) and ¹H nuclear magnetic resonance (NMR).

The preliminary evaluation indicates that these systems are promising analytical tools for the selective detection of nickel (II), even alongside competing metal ions. This study provides a basis for the further development of practical applications in real-time environmental monitoring and chemical detection.